| 1. |
- Abeysinghe, Kasun S., et al.
(författare)
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Mercury flow through an Asian rice-based food web
- 2017
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Ingår i: Environmental Pollution. - : ELSEVIER SCI LTD. - 0269-7491 .- 1873-6424. ; 229, s. 219-228
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Tidskriftsartikel (refereegranskat)abstract
- Mercury (Hg) is a globally-distributed pollutant, toxic to humans and animals. Emissions are particularly high in Asia, and the source of exposure for humans there may also be different from other regions, including rice as well as fish consumption, particularly in contaminated areas. Yet the threats Asian wildlife face in rice-based ecosystems are as yet unclear. We sought to understand how Hg flows through rice-based food webs in historic mining and non-mining regions of Guizhou, China. We measured total Hg (THg) and methylmercury (MeHg) in soil, rice, 38 animal species (27 for MeHg) spanning multiple trophic levels, and examined the relationship between stable isotopes and Hg concentrations. Our results confirm biomagnification of THg/MeHg, with a high trophic magnification slope. Invertivorous songbirds had concentrations of THg in their feathers that were 15x and 3x the concentration reported to significantly impair reproduction, at mining and non-mining sites, respectively. High concentrations in specialist rice consumers and in granivorous birds, the later as high as in piscivorous birds,, suggest rice is a primary source of exposure. Spiders had the highest THg concentrations among invertebrates and may represent a vector through which Hg is passed to vertebrates, especially songbirds. Our findings suggest there could be significant population level health effects and consequent biodiversity loss in sensitive ecosystems, like agricultural wetlands, across Asia, and invertivorous songbirds would be good subjects for further studies investigating this possibility.
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| 2. |
- Campeau, Audrey, et al.
(författare)
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Sources of riverine mercury across the Mackenzie River Basin; inferences from a combined Hg C isotopes and optical properties approach
- 2022
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Ingår i: Science of the Total Environment. - : Elsevier BV. - 0048-9697 .- 1879-1026. ; 806, s. 150808-150808
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Tidskriftsartikel (refereegranskat)abstract
- The Arctic terrestrial environment harbors a complex mosaic of mercury (Hg) and carbon (C) reservoirs, some of which are rapidly destabilizing in response to climate warming. The sources of riverine Hg across the Mackenzie River basin (MRB) are uncertain, which leads to a poor understanding of potential future release. Measurements of dissolved and particulate mercury (DHg, PHg) and carbon (DOC, POC) concentration were performed, along with analyses of Hg stable isotope ratios (incl. ∆199Hg, d202Hg), radiocarbon content (∆14C) and optical properties of DOC of river water. Isotopic ratios of Hg revealed a closer association to terrestrial Hg reservoirs for the particulate fraction, while the dissolved fraction was more closely associated with atmospheric deposition sources of shorter turnover time. There was a positive correlation between the ∆14C-OC and riverine Hg concentration for both particulate and dissolved fractions, indicating that waters transporting older-OC (14C-depleted) also contained higher levels of Hg. In the dissolved fraction, older DOC was also associated with higher molecular weight, aromaticity and humic content, which are likely associated with higher Hg-binding potential. Riverine PHg concentration increased with turbidity and SO4 concentration. There were large contrasts in Hg concentration and OC age and quality among the mountain and lowland sectors of the MRB, which likely reflect the spatial distribution of various terrestrial Hg and OC reservoirs, including weathering of sulfate minerals, erosion and extraction of coal deposits, thawing permafrost, forest fires, peatlands, and forests. Results revealed major differences in the sources of particulate and dissolved riverine Hg, but nonetheless a common positive association with older riverine OC. These findings reveal that a complex mixture of Hg sources, supplied across the MRB, will contribute to future trends in Hg export to the Arctic Ocean under rapid environmental changes.
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| 3. |
- Larsson, Tom, 1974-
(författare)
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Instrumental and methodological developments for isotope dilution analysis of gaseous mercury species
- 2007
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- This thesis deals with instrumental and methodological developments for speciation analysis of gaseous mercury (Hg(g)), based on isotope dilution analysis (IDA). The studied species include Hg0, (CH3)2Hg, CH3HgX and HgX2 (where X symbolises a negatively charged counter ion in the form of a halide or hydroxyl ion). Gas chromatography hyphenated with inductively coupled plasma mass spectrometry (GC-ICPMS) was used for separation and detection of Hg(g) species. Permeation tubes were used for the generation of gaseous isotopically enriched Hg standards (tracers). These tracers were continuously added to the sample gas stream during sampling of Hg(g). A mobile prototype apparatus incorporating both the permeation source and a sampling unit for collection of Hg(g) was developed and used for this purpose. Hg(g) species were pre-concentrated on Tenax TA and / or Carbotrap solid adsorbents. Au-Pt was used for pre-concentration of total Hg(g), either as the primary medium, or as backup. Collected species were eluted from these media and introduced to the instrument by thermal desorption. Various degrees of species transformations, as well as losses of analyte during pre-concentration and elution, were found to occur for both Tenax TA and Carbotrap. The performance characteristics of these media were shown to be species specific, as well as matrix dependent. The development of an on-line derivatisation procedure allowed for minimised species transformations, as well as reduced adsorption and memory effects of ionic Hg(g) species within the analytical system. In conclusion, IDA provides an important tool for identification, minimisation and correction of the above mentioned analytical problems. Furthermore, it offers significant advantages with respect to quality assurance, compared to conventional techniques, both when it comes to rational development of new methodology, as well as for continuous validation of existing procedures. The developed methodology for speciation analysis of Hg(g) has been tested in various applications, including the determination of Hg(g) species concentrations in ambient air (both in and outdoor) and in the head space of sediment microcosms. Hg(g) species were formed in the sediments as a result of naturally occurring redox and methylation processes, after addition of an isotope enriched aqueous Hg(II) precursor. The methodology has also been used for assessing the risk of occupational exposure to Hg(g) species during remediation of a Hg contaminated soil and for studying Hg0(g) transport and Au-Pt pre-concentration characteristics in natural gases. Hg0 was used as the model species in the latter experiments, since it is believed to be the dominating form of Hg(g) in natural gas. The results indicate that the occurrence of H2S can cause temperature dependent adsorption and memory effects of Hg0(g) in the presence of stainless steel, thereby providing a plausible explanation to the variability of results for sour gases occasionally observed in the field. Hg0(g) has demonstrated overall high recovery during collection on Au-Pt tubes for all gases tested in this thesis. Recent (unpublished) results however indicate that there are potential species specific and matrix dependent effects associated with the Au-Pt based pre-concentration of Hg(g) in natural gases.
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| 4. |
- Yuan, Shengliu, et al.
(författare)
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Insight into the Hg sources by stable isotopes of mercury in the largest Arctic river in North America
- 2020
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Konferensbidrag (refereegranskat)abstract
- Mercury (Hg), especially in its methylated form (MeHg), is a global environmental toxicant with the threat to wildlife and humans. Although the Arctic is void of anthropogenic Hg emission,the elevated Hg content in the Arctic food web shows the significant impact of global Hg contamination. Besides the atmospheric input, the Arctic rivers may also deliver a large amount of Hg, 44 ± 4 Mg per year (1σ) by observations and extrapolation, intothe Arctic Ocean. However, the contributions of different sources to riverine discharge remain mostly unknown. This makes it challenging to reduce the anthropogenic Hg emission in the future, since this is messed by the natural Hg, including the precipitation Hg and the released Hg of permafrost thaw in response to the global warming. To anticipate the risk of Hg contamination in Arctic ecosystems, it is vital to identify the sources in the Arctic riverine. Here,we collected and analyzed the set of river samples in Mackenzie River, the largest Arctic river in North America. The Hg concentrations and isotopic compositions show the spatial and temporal distribution, with the higher concentrations the particle Hg than dissolved Hg and the higher concentrations in downstream than upstream. Notably, the significant difference of Hg isotopic compositions between the particle and dissolved Hg, coupling with the carbon isotopes, shows that the atmospheric precipitation Hg is the primary source of the dissolved phase, higher proportion Hg of permafrost Hg contributes to the particulate Hg. This constraint of the Hg sources will be conducive to evaluate the future risk to Arctic aquatic ecosystems under the background of global climate warming.
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| 5. |
- Zdanowicz, Christian, 1966-, et al.
(författare)
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Identifying terrestrial sources of mercury in streams of the Mackenzie River Basin, NW Canada
- 2019
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Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- The Mackenzie River, with a catchment >1 million km^2 and a mean water discharge of 10,000 m^3/s, is the largest conduit for freshwater and sediment delivery to the Beaufort Sea. During peak flow, the Mackenzie and its main tributaries have some of the highest Hg levels in freshwaters of the Canadian Arctic and subarctic (>> 10 ng/L). An unknown fraction of this Hg is derived from thawing permafrost soils in the northern reaches of the Mackenzie basin. This contribution is likely to increase as NW Canada warms up over the next decades at nearly twice the mean rate of the whole country. To better anticipate the future impact of warming on riverine Hg transfer to the Beaufort Sea marine ecosystem, a Swedish-Canadian research project was initiated to identify and quantify the terrestrial sources of Hg in streams of the Mackenzie basin. Water was sampled from the Mackenzie itself and selected tributaries during spring peak flow in 2018, and will also be sampled during the base flow period in 2019. Water samples are being analysed for isotopic ratios of O and H in water, C and Hg (dissolved and particulate), as well as the optical properties of dissolved organic matter, to help in the source apportionment of Hg between various terrestrial pools such as rocks and organic soils. These data will be used to constrain a mixing model of water properties, including Hg loads, created for the Mackenzie drainage system. The mixing model will be used to simulate future riverine Hg transfer rates to the Beaufort Sea under varying scenarios of Hg release from the different terrestrial reservoirs, such as permafrost soils. The study design, methods, and preliminary findings will be presented.
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| 6. |
- Zdanowicz, Christian M., et al.
(författare)
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Historical variations of mercury stable isotope ratios in arctic glacier firn and ice cores
- 2016
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Ingår i: Global Biogeochemical Cycles. - 0886-6236 .- 1944-9224. ; 30:9, s. 1324-1347
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Tidskriftsartikel (refereegranskat)abstract
- The concentration and isotopic composition of mercury (Hg) were determined in glacier core samples from Canadian Arctic ice caps dating from pre-industrial to recent time (early 21st century). Mean Hg levels increased from ≤ 0.2 ng L-1 in pre-industrial time to ~0.8-1.2 ng L-1 in the modern industrial era (last ~200 years). Hg accumulated on Arctic ice caps has D199Hg and D201Hg that are higher (~-1 to 2.9 ‰) than previously reported for Arctic snow (mostly < -1 ‰) impacted by atmospheric Hg depletion events, suggesting that these events contribute little to Hg accumulation on ice caps. The range of d202Hg, D199Hg and D201Hg in glacier cores overlaps with that of Arctic Hg0(g) and of seawater in Baffin Bay, but also with that of mid-latitude precipitation and industrial Hg sources, including coal and Hg ores. A core from Agassiz ice cap (80.7 °N) shows a ~+1 ‰ shift in d202Hg over the 19th-20th centuries that could reflect changes in the isotopic composition of the atmospheric Hg pool in the High Arctic in response to growing industrial emissions at lower latitudes. This study is the first ever to report on historical variations of Hg stable isotope ratios in Arctic ice cores. Results could help constrain future modeling efforts of the global Hg biogeochemical cycle and the atmosphere's response to changing Hg emissions, past and future.
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| 7. |
- Zdanowicz, Christian, 1966-, et al.
(författare)
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Mercury inputs to the Mackenzie River and the Beaufort Sea: : Future impacts of permafrost thaw
- 2019
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Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- Recent studies highlighted the existence of a large reservoir of mercury (Hg) stored in frozen soils and peat of the circum-Arctic, and evidence is accumulating that this Hg is being released by permafrost thaw to streams and lakes in the northern Yukon and Northweest Territories. This raises the question whether such releases will increase the net export of Hg by large Arctic rivers to marginal seas of the Arctic Ocean, and thus potentially negating some of the long-term environmental benefits of Hg emissions reductions under the UN Minamata convention. In 2018 we initiated a Swedish-Canadian research project to investigate the sources of Hg entering the Mackenzie River, using an approach that combines measurements of multiple water quality parameters, including isotopes of Hg and carbon (dissolved and particulate). We carried out a sampling survey across the Mackenzie River Basin (MRB) in the summer of 2018, and will extend this with additional sampling in 2019. We will present our initial findings from this study, with a focus on the implications for climate change on the cycling of terrestrial Hg between the MRB and Beaufort Sea.
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| 8. |
- Zdanowicz, Christian, 1966-, et al.
(författare)
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Pre-industrial and recent (1970-2010) atmospheric deposition of sulfate and mercury in snow on southern Baffin Island, Canada
- 2015
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Ingår i: Science of the Total Environment. - : Elsevier BV. - 0048-9697 .- 1879-1026. ; 509-510, s. 104-114
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Tidskriftsartikel (refereegranskat)abstract
- Sulfate (SO4) and mercury (Hg) are airborne pollutants transported to the Arctic where they can affect properties of the atmosphere and the health of marine or terrestrial ecosystems. Detecting trends in Arctic Hg pollutionis challenging because of the short period of direct observations, particularly of actual deposition. Here, we presentan updated proxy record of atmospheric SO4 and a new 40-year record of total Hg (THg) and monomethyl Hg (MeHg) deposition developed from a firn core (P2010) drilled from Penny Ice Cap, Baffin Island, Canada. The updated P2010 record shows stable mean SO4 levels over the past 40 years, which is inconsistent with observations of declining atmospheric SO4 or snow acidity in the Arctic during the same period. A sharp THg enhancement in the P2010 core ca 1991 is tentatively attributed to the fallout from the eruption of the Icelandic volcano Hekla. Although MeHg accumulation on Penny Ice Cap had remained constant since 1970, THg accumulation increased after the 1980s. This increase is not easily explained by changes in snow accumulation, marine aerosol inputs or air mass trajectories; however, a causal link may exist with the declining sea-ice cover conditions in the Baffin Bay sector. The ratio of THg accumulation between pre-industrial times (reconstructed from archived ice cores) and the modern industrial era is estimated at between 4- and 16-fold, which is consistent with estimates from Arctic lake sediment cores. The new P2010 THg record is the first of its kind developed from the Baffin Island region of the eastern Canadian Arctic and one of very few such records presently available in the Arctic. As such, it may help to bridge the knowledge gap linking direct observation of gaseous Hg in theArctic atmosphere and actual net deposition and accumulation in various terrestrial media.
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